Tiltrotor aircraft, such as the Bell Boeing V-22 Osprey and Bell V-280 Valor, have proprotors on opposing sides of the aircraft that are selectively pivotable between a vertical orientation for rotor-borne flight (helicopter mode) and a horizontal orientation for wing-borne flight (airplane mode). Typically, each proprotor is driven in rotation by an associated propulsion assembly, comprising an engine, a gearbox, and a transmission. The transmissions of the propulsion assemblies are connected with an interconnect driveshaft to allow the engine of one propulsion assembly to drive rotation of both proprotors, thus providing redundancy and allowing for continued flight if the engine of either propulsion assembly becomes inoperative.